The invention relates to supply of power to a resonator by voltages greater than 200 V and frequencies higher than 1 MHz and in particular to the supply of power to resonators used in controlled ignitions.
For application to automobile plasma ignition, resonators whose resonant frequency is higher than 1 MHz are arranged at the spark plug and are typically supplied with voltages greater than 200 V and are subjected to a current greater than 10 A. This application necessitates the use of radiofrequency resonators with a high quality factor and a high voltage generator, the operating frequency of which is very close to the resonant frequency of the resonator. The more the difference between the resonant frequency of the resonator and the operating frequency of the generator is reduced, the higher the amplification factor (ratio of its output voltage to its input voltage) of the resonator. The higher the quality factor of the resonator, the more the operating frequency of the generator must be close to its resonant frequency.
Numerous parameters have an impact on the resonant frequency: manufacturing tolerances, temperature in the combustion chamber or in the cooling circuit, or aging drift in the resonator components. These parameters have an even more significant impact for the particular case of spark plug coils due to the proximity between certain components of the resonator and the combustion chamber. Guaranteeing an amplification factor of the resonator is hence a delicate matter.